What lights indicate that a school bus is picking up or dropping off children?

The correct answer highlights the use of flashing red lights and an extended stop arm as critical indicators that a school bus is actively picking up or dropping off children. These visual signals are designed to alert other drivers that they must stop and maintain a safe distance from the bus. This is vital for ensuring the safety of children who are boarding or disembarking from the vehicle.

When the bus activates its flashing red lights, it communicates to surrounding traffic that the bus is halted for the purpose of allowing children to enter or exit. The extended stop arm further reinforces this message, visibly indicating to drivers that they must not pass the bus while it is loading or unloading passengers. Both of these features are requirements under state laws and are intended to create a safe environment for children during these critical moments.

The other options do not provide adequate safety measures associated with school bus operations. Flashing yellow lights and hazard lights might suggest caution or an upcoming stop but do not convey the immediate need to halt. Flashing white lights are typically used in different contexts, such as emergency or construction vehicles, and solid green lights would indicate permission to go, which does not serve the safety of children at a school bus stop.